Radio communication system, radio apparatus, radio communication method, packet generation method, and method for reproducing data from packet

ABSTRACT

When operating the radio communication system in a mode for transmitting data for data communication instead of audio signal data, a transmission unit of a radio apparatus generates a packet in which data for data communication is inserted in positions in an audio frame, except for a given position, and in a data frame, and unique data is inserted in the given position in the audio frame. Also, data that is likely to cause an error when the data inserted in the audio frame is decoded by using an audio codec is used as the unique data.

CROSS REFERENCE TO RELATED APPLICATIONS

The disclosure of Japanese Patent Application serial No. 2015-30810,filed on Feb. 19, 2015, including the specification, drawings andabstract is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a radio communication system employingdigital audio communication, a radio apparatus used in the system, and aradio communication method, a packet data generation method, and amethod for reproducing data from a packet, which correspond to thesystem.

Description of the Related Art

In recent years, a digitized and networked environment for audiocommunication has been developing in the field of amateur radio forexample, so that the users can enjoy communication at higher speed andexchange clearer audio messages. In a radio communication systememploying such digital audio communication, audio signals are encodedand converted into digital signals, and are transmitted after beingpacketized (for example, see JP 2006-157477A).

In the aforementioned radio communication system, data indicating callsigns of the transmission destination and the transmission source, etc.are added to the header part of the packet, and accordingly the systemcan achieve many functions such as the function of performingcommunication with the designation of the communication party radioapparatus, which cannot be achieved by analogue radio communicationsystems.

Furthermore, according to the aforementioned radio communication system,audio frames and data frames, each having a predetermined length, areconsecutively arranged one after the other, so that data for audiocommunication and data for data communication can be simultaneouslytransmitted.

Therefore, with use of this function, image signals captured by a cameracan be transmitted from one radio apparatus to another radio apparatusduring communication, so that the image is displayed on a display andthe users can enjoy a conversation while seeing the image, for example.

However, the aforementioned conventional radio communication system isdesigned for audio communication, and the amount of data that can betransmitted in data communication is set to be smaller than the amountof data that can be transmitted by audio communication, and accordinglythe communication speed of the data communication is not necessarilyhigh.

BRIEF SUMMARY OF THE INVENTION

In order to increase the communication speed of data communicationaccording to the above-described radio communication system, theinventors, etc., of the present invention proposed to insert data fordata communication into audio frames used for transmitting audio signaldata, and to thus transmit data for data communication. The presentinvention is made in relation to this proposal.

In the following description, the communication mode in which audiosignal data is inserted into audio frames is referred to as “slow datamode”, and the communication mode in which data for data communicationis inserted into audio frames is referred to as “fast data mode”, basedon the difference in the communication speed of data communication.

In the case where a packet in which a data signal for data communicationis inserted in the above-described audio frames is received by anexisting radio apparatus that does not support the fast data mode, datafor data communication inserted in the audio frames is decoded as audiodata, and is output as an abnormal sound from the speaker. Therefore,the proposal above cannot be adopted as it is in such a case.

The present invention is made in view of such a situation, and aims toprovide a radio communication system, a radio apparatus, a radiocommunication method, a packet generation method, and a method forreproducing data from a packet, by which, even in the case where anexisting radio apparatus that does not support the fast data modereceives a packet in which a data signal for data communication isinserted in the audio frames, the abnormal sound can be reduced to sucha level that is not problematic in practical use.

To achieve the aim above, a radio communication system according to thepresent invention is a radio communication system including at least tworadio apparatuses,

each radio apparatus comprising:

a transmission unit configured to generate a packet including: a headerpart containing identifier data identifying at least a transmissiondestination radio station and a transmission source radio station; and adata part in which an audio frame and a data frame, each having apredetermined length, are consecutively arranged one after another, toinsert audio signal data into the audio frame of the packet and toinsert data other than the audio signal data into the data frame of thepacket, and to thereafter convert the packet into a radio signal andtransmit the radio signal;

a reception unit configured to receive the radio signal, to reproduce apacket from the radio signal, to retrieve the audio signal data from theaudio frame of the packet, and to retrieve the data other than the audiosignal data from the data frame of the packet;

an audio codec configured to generate a digital audio signal byperforming A/D conversion and encoding on an analogue audio signal andthereafter transmit the digital audio signal to the transmission unit,and to reproduce an analogue audio signal by performing decoding and D/Aconversion on a digital audio signal received from the reception unit;and

a controller configured to instruct the transmission unit to generate apacket, and to instruct the reception unit to reproduce a packet from areceived radio signal,

wherein, when communication is performed in a fast data mode in whichdata for data communication to be transmitted, instead of audio signaldata, is inserted in the audio frame,

the transmission unit of a radio apparatus serving as a sender,generates according to an instruction from the controller, a packet inwhich the data for data communication is inserted in positions in theaudio frame, excluding a given position, and in the data frame, andunique data is inserted in the given position in the audio frame, and

the controller of a radio apparatus serving as a recipient, which hasreceived a radio signal, instructs the reception unit to retrieve dataportions other than the unique data from the audio frame and the dataframe of the packet, which has been reproduced, and reproduces the datafor data communication by concatenating the retrieved data portions.

A radio apparatus according to the present invention is a radioapparatus comprising:

a transmission unit configured to generate a packet including: a headerpart containing identifier data identifying at least a transmissiondestination radio station and a transmission source radio station; and adata part in which an audio frame and a data frame, each having apredetermined length, are consecutively arranged one after another, toinsert audio signal data into the audio frame of the packet and toinsert data other than the audio signal data into the data frame of thepacket, and to thereafter convert the packet into a radio signal andtransmit the radio signal;

an audio codec configured to generate a digital audio signal byperforming A/D conversion and encoding on an analogue audio signal andthereafter transmit the digital audio signal to the transmission unit;and

a controller configured to instruct the transmission unit to generate apacket,

wherein, when operating in a fast data mode in which data for datacommunication to be transmitted, instead of audio signal data, isinserted in the audio frame,

the transmission unit generates, according to an instruction from thecontroller, a packet in which the data for data communication isinserted in positions in the audio frame, excluding a given position,and in the data frame, and in which unique data is inserted in the givenposition in the audio frame.

A radio communication method according to the present invention is aradio communication method for a radio communication system including atleast two radio apparatuses, one of the at least two radio apparatusesbeing configured to generate a packet including: a header partcontaining identifier data identifying at least a transmissiondestination radio station and a transmission source radio station; and adata part in which an audio frame and a data frame, each having apredetermined length, are consecutively arranged one after another, andto convert the packet into a radio signal and transmit the radio signal,and another one of the at least two radio apparatuses being configuredto receive the radio signal and reproduce a packet from the receivedradio signal, the radio communication method comprising the steps of:

in a radio apparatus serving as a sender,

-   -   generating a packet in which data for data communication is        inserted in positions in the audio frame, excluding a given        position, and in the data frame, and unique data is inserted in        the given position in the audio frame; and    -   converting the packet thus generated into a radio signal, and        transmitting the radio signal, and

in a radio apparatus serving as a recipient,

-   -   receiving the radio signal;    -   reproducing a packet from the received radio signal;    -   retrieving data portions other than the unique data from the        audio frame and the data frame of the reproduced packet; and    -   reproducing data for data communication by concatenating the        retrieved data portions.

A packet generation method according to the present invention is apacket generation method for a radio apparatus that performscommunication with another radio apparatus by using a packet including:a header part containing identifier data identifying at least atransmission destination radio station and a transmission source radiostation; and a data part in which an audio frame and a data frame, eachhaving a predetermined length, are consecutively arranged one afteranother, the packet generation method comprising the step of:

generating a packet in which data for data communication is inserted inpositions in the audio frame, excluding a given position, and in thedata frame, and unique data is inserted in the given position in theaudio frame.

A method for reproducing data from a packet according to the presentinvention is a method for reproducing data from a packet performed by aradio apparatus that is configured to receive a radio signal containinga packet generated by the above-described packet generation method andreproduces the packet from the radio signal, the method comprising thesteps of:

retrieving data portions other than the unique data from the audio frameand the data frame of the reproduced packet; and

reproducing the data for data communication by concatenating theretrieved data portions.

By using the radio communication system according to the presentinvention, even in the case where an existing radio apparatus that doesnot support the fast data mode receives a packet in which data for datacommunication is inserted in the audio frames, the abnormal soundgenerated by the speaker can be reduced to such a level that is notproblematic in practical use.

Consequently, even in the case of using a mix of an existing radioapparatus that performs communication in the slow data mode and a radioapparatus that supports the fast data mode, to which the function ofinserting a data signal for data communication into audio frames andtransmitting the data signal is added, communication can be performedwithout a problem.

Also, the functions realized by the above-described radio communicationsystem can be realized by the radio apparatus, the radio communicationmethod, the packet generation method, and the method for reproducingdata from a packet according to the present invention, with a similarconfiguration or method.

These and other objects, features and advantages of the presentinvention will become more apparent upon reading of the followingdetailed description along with the accompanied drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a configuration of a radio apparatusused in a radio communication system according to an embodiment of thepresent invention.

FIG. 2 is a diagram showing a configuration of a packet transmitted bythe radio apparatus.

FIG. 3 is a diagram showing types of data to be inserted in frames ofthe data part of a packet.

FIG. 4 is a diagram showing an arrangement of radio apparatuses andrepeaters in a radio communication system according to the embodiment ofthe present invention.

FIG. 5A and FIG. 5B are diagrams respectively showing a configuration ofan audio frame in a slow data mode and a configuration of an audio framein a fast data mode.

FIG. 6 is a flowchart showing processing performed by a controller of aradio apparatus that has received a packet.

DETAILED DESCRIPTION OF THE INVENTION

The following describes a radio communication system according to anembodiment of the present invention, with reference to the drawings.

Configuration of Radio Apparatus

FIG. 1 shows a configuration of a radio apparatus used in a radiocommunication system according to the present embodiment. A radioapparatus 1 includes a microphone 11, a speaker 12, an AF amplificationunit 13, an audio codec 14, a transmission unit 15, atransmission/reception switching unit 16, an antenna 17, a receptionunit 18, an interface unit 19, a controller 21, an operation unit 26,and a display unit 28. In the drawing, thick arrows indicate the flow ofan audio signal, data, etc., and thin arrows indicate the flow of acontrol system signal.

The microphone 11 generates an analogue audio signal from input audio tobe transmitted, and outputs the audio signal to the AF amplificationunit 13. The speaker 12 converts an analogue audio signal output fromthe AF amplification unit 13, to a sound.

The AF (Audio Frequency) amplification unit 13 amplifies an analogueaudio signal input from the microphone 11, and supplies the resultantsignal to the audio codec 14. The AF amplification unit 13 alsoamplifies an analogue audio signal of reception sound supplied from theaudio codec 14, and outputs the resultant signal to the speaker 12.

The audio codec 14 performs A/D (analogue/digital) conversion andencoding on an analogue audio signal supplied from the AF amplificationunit 13, and outputs the resultant signal to the transmission unit 15.The audio codec 14 also decodes, and furthermore performs D/A(digital/analogue) conversion on, a digital audio signal supplied fromthe reception unit 18, and outputs the resultant signal to the AFamplification unit 13.

The transmission unit 15 adds a header for radio communication to adigital audio signal supplied from the audio codec 14, and alsogenerates a packet for transmission as shown in FIG. 2, based on anoutput from a PTT switch 27 described later. The configuration of thepacket will be described later in detail with reference to FIG. 2. Thetransmission unit 15 furthermore modulates a carrier wave by usingdigital data contained in the packet, and transmits the resultant wavefrom the antenna 17 via the transmission/reception switching unit 16.

The transmission/reception switching unit 16 delivers the transmissionsignal from the transmission unit 15 to the antenna 17 when the PTTswitch 27 is pressed and turned ON, and delivers the reception signal ofthe antenna 17 to the reception unit 18 when the PTT switch 27 isreleased and turned OFF.

The reception unit 18 changes the reception frequency according to aninstruction signal from the controller 21, amplifies the receptionsignal obtained by tuning to the reception frequency, and furthermore,demodulates the resulting signal to reproduce a packet. Then, thereception unit 18 removes the header part from the reproduced packet,and supplies the audio signal data to the audio codec 14 and suppliesthe other data (e.g., packet data of an image signal, etc.) to theinterface unit 19.

The interface unit 19 is connected to an external device 31 (e.g., apersonal computer or a smartphone) via an external connection terminal20 and to a device 32 (e.g., a GPS receiver) that is built into theradio apparatus, and supplies packet data supplied from the externaldevice 31 and the built-in device 32, such as an image signal, to thetransmission unit 15 and the controller 21. The interface unit 19 alsosupplies packet data supplied from the reception unit 18, to theexternal device 31 via the external connection terminal 20.

The controller 21 controls the operation of the radio apparatus 1. Thecontroller 21 includes a CPU (Central Processing Unit) 22, a ROM (ReadOnly Memory) 23 storing a program operating on the CPU 22, a RAM (RandomAccess Memory) 24 serving as a work memory for the CPU 22, and anon-volatile memory 25 storing data such as a call sign. Although notdescribed every time, an instruction from the controller 21 to each unitis made by transmitting a command.

The operation unit 26 conveys various sorts of inputs and userinstructions to the controller 21. The operation unit 26 includes thePTT (Push To Talk) switch 27 and a mode switch 33 that is for switchingbetween communication modes. When the PTT switch 27 is pressed (turnedON), the transmission/reception switching unit 16 switches to thetransmission mode and a transmission from the antenna 17 is performed,and when the PTT switch 27 is released (turned OFF), thetransmission/reception switching unit 16 switches to the reception modeand the reproduction of the received audio signal is performed.

The display unit 28 includes a liquid crystal display or the like, andis used for displaying various sorts of data. The screen of the displayunit 28 displays, for example, information indicating that the radioapparatus 1 has received amateur radio signals (there has been a call),and call signs or nicknames of the transmission source (the user's ownstation) and the transmission destination (the communication partystation).

Configuration of Packet

Next, with reference to FIG. 2 and FIG. 3, a description is given of theconfiguration of a packet generated by the transmission unit 15. Theconfiguration of the packet shows the order and the grouping of a seriesof data pieces to be transmitted in digital audio communication.

As shown in FIG. 2, a packet Pa includes a header part Ph and a datapart Pd. The header part Ph includes a synchronization signal h1, a flagh2, a transmission destination repeater call sign h3, a transmissionsource repeater call sign h4, a transmission destination call sign h5,and a transmission source call sign h6.

The synchronization signal h1 in the header part Ph is used forsynchronization with the reception signal, and indicates the startingpoint of the signal. The flag h2 is data for indicating communicationvia a repeater, direct communication, a repeater control signal, etc.,and is composed of a plurality of bits.

The transmission destination repeater call sign h3 is, for example, thecall sign of a repeater station within the repeater area to which thetransmission destination radio station belongs, and the transmissionsource repeater call sign h4 is a call sign of a repeater station withinthe repeater area to which the transmission source radio stationbelongs. The transmission destination call sign h5 is the call sign ofthe communication party station at the destination of the transmission,and the transmission source call sign h6 is the call sign of the user'sown station. These call signs (h3 to h6) serve as identifiers foridentifying the radio stations at the transmission destination and thetransmission source, as well as the repeater stations that relay theradio signals. Note that the transmission destination call sign h5 maybe CQ for making a call without the designation of any particularstation.

In order to achieve the simultaneous transmission of data for audiocommunication and data for data communication, the data part Pd includesaudio frames d1 and data frames d2, which are arranged one after theother, and a clearing frame d3 is attached to the end. Each of the audioframes d1 has a predetermined length, and a digitized audio signal isinserted into it. Each of the data frames d2 has a predetermined length,and data sets for data communication such as an image signal and amessage are inserted into it. The clearing frame d3 indicates the end ofthe packet.

Note that the data frames d2 are periodically replaced with aresynchronization frame d4 (e.g. every 420 ms). A synchronization signalfor synchronization with the radio apparatus of the communication partystation is inserted into each resynchronization frame d4.

Next, with reference to FIG. 3, a description is given of data for datacommunication, which is to be inserted into the data frames d2. FIG. 3shows the types of data to be inserted into each frame of the data partPd. In this drawing, “audio” shows that audio signal data is inserted inthe frame, and “data” shows that data for data communication is insertedin the frame.

Regarding the audio frames d1 and the data frames d2 constituting thedata part Pd, the data amount of the audio frames d1 is set to begreater than the data mount of the data frames d2, because thetransmission of audio signal data is given a high priority. Usually, 9bytes of data is inserted into each of the audio frames d1, and 3 bytesof data is inserted into each of the data frames d2.

Furthermore, a mini-header d5, which includes the description of thedata type, etc., is inserted in the beginning of the data frame d2.However, if the mini-header d5 is provided in every data frame, theamount of data that can be inserted in the data frame will be smaller,and therefore one mini-header d5 is inserted in one data frame out ofevery two data frames.

Therefore, as shown in FIG. 3 at the lower level, when generating thepacket Pa, communication data d6 for data communication is divided into5-byte portions, and 1-byte mini-header d5 is added to the beginning ofeach portion so as to compose a data block, and after that, the datablock is divided into 3-byte portions, and these portions arerespectively inserted into two adjacent data frames d2.

Then, information indicating the data type and the data length iswritten into each mini-header d5. The data length indicates the lengthof the effective data inserted in a single data block. For example,suppose the case of transmitting general-purpose data having a datalength of 13 bytes, such as image data. First, when the data to betransmitted is divided into 5-byte portions as described above, the datawill be divided into three portions, namely 5-byte portion, 5-byteportion, and 3-byte portion. Then, the mini-header d5 is added to thebeginning of each of these data portions. Here, if the informationindicating the general-purpose data such as image data is 0x3 forexample, the mini-header d5 added to each of the first and second datablocks is 0x35, and the mini-header d5 added to the third data block is0x33.

The controller 21 (see FIG. 1) retrieves, via the interface unit 19, thedata indicating the data type, etc., from the data for datacommunication transmitted from an external device connected to theterminal 20, and stores the retrieved data to the RAM 24. Also, when thetransmission unit 15 generates packets for transmission, the controller21 reads the aforementioned data from the RAM 24 and transfers it to thetransmission unit 15. In the transferred data, the informationindicating the data type is written into the mini-header d5.

Meanwhile, when reproducing the data for data communication from thepackets Pa reproduced by the reception unit 18, the reverse of theaforementioned process is performed, i.e., based on the information inthe mini-header d5, a 5-byte communication data portion is retrievedfrom the data contained in two data frames d2, the data for datacommunication is reproduced by concatenating the 5-byte communicationdata portions with each other, and the data for data communication istransmitted to an external device via the interface unit 19.

Operations for Communication in Slow Data Mode

As described above, the radio communication system according to thepresent embodiment can perform communication in two modes, the slow datamode and the fast data mode. First, a description is given of theoperations for communication in the slow data mode, with reference toFIG. 1 to FIG. 3.

The operation unit 26 has a mode switch 33 for switching between thecommunication modes, and the user can select either the slow data modeor the fast data mode by operating the switch 33. The slow data mode isselected when communication is performed with a conventional radioapparatus that has no option for a communication mode, or when no datafor data communication needs to be transmitted, for example. Note that,the mode switch 33 may be other than the switch. For example, switchingbetween the modes may be instructed from a menu screen displayed when amenu button or the like is pressed.

As a typical case where the slow data mode is used, the followingdescribes the case where a radio station (the user's own station) withina given repeater area makes a call to a radio station (the communicationparty station) within another repeater area.

FIG. 4 shows an arrangement of radio apparatuses and repeaters in aradio communication system according to the present embodiment. A radiocommunication system 100 includes at least two radio apparatuses 1 andat least one repeater 3. In the example shown in FIG. 4, radioapparatuses 1 a, 1 b, and 1 c exist within an area 2 a covered by arepeater 3 a, and radio apparatuses 1 d and 1 e exist within an area 2 bcovered by a repeater 3 b. The adjacent repeaters 3 a and 3 b transmitaudio and data in a multiplexed state to each other by using microwaves.

The following describes a case in which the radio apparatus 1 a withinthe area 2 a and the radio apparatus 1 d within the area 2 b communicatewith each other. Before starting the communication, the user operatesthe operation unit 26 of the radio apparatus 1 a in order to store, tothe non-volatile memory 25, information necessary for the communication,such as the call sign of the transmission source (the user's ownstation) and the call signs of the repeater stations.

When starting the communication, the user operates the operation unit 26of the radio apparatus 1 a in order to make a call with the designationof the call sign given to the transmission destination radio station andthe call sign of the transmission destination repeater.

When the user presses the PTT switch 27, the information input from theoperation unit 26 is provided to the transmission unit 15 by thecontroller 21, and the transmission unit 15 generates a packet accordingto an instruction from the controller 21. As shown in FIG. 2, the headerpart Ph of the packet Pa contains the call sign h3 of the transmissiondestination repeater, the call sign h4 of the transmission sourcerepeater, the call sign h5 of the transmission destination (thecommunication party station), and the call sign h6 of the transmissionsource (the user's own station).

Within the data part Pd of the packet Pa, audio signal data output fromthe audio codec 14 is inserted into the audio frames d1, and data fordata communication transferred from the interface unit 19 is insertedinto the data frames d2.

The packet Pa generated and converted into radio signals by thetransmission unit 15 are transmitted via the transmission/receptionswitching unit 16 and the antenna 17. The packet Pa transmitted by theradio apparatus 1 a (the user's own station) is relayed by the repeaters3 a and 3 b, and reaches the radio apparatus 1 d (the communicationparty station).

The radio signals received by the radio apparatus 1 d (the communicationparty station) are provided to the reception unit 18 via the antenna 17and the transmission/reception switching unit 16, and are demodulated bythe reception unit 18, and thus the packet Pa is reproduced.Furthermore, the header part Ph is removed from the packet Pa reproducedby the reception unit 18, and the data in the data part Pd is providedto the audio codec 14 or the interface unit 19, depending on thecontents of the data.

Audio signal data provided to the audio codec 14 is decoded, and isfurthermore converted into an analogue audio signal, and is thenprovided to the AF amplification unit 13. The audio signal amplified bythe AF amplification unit 13 is output from the speaker 12, and thus thevoice of the user of the transmission source is reproduced.

In contrast, the data for data communication obtained by demodulatingthe packet shown in FIG. 3 is transferred to an external device 31 viathe interface unit 19.

Furthermore, the packet Pa reproduced by the reception unit 18 isprovided to the controller 21. The CPU 22 of the controller 21determines whether or not the packet Pa thus received is a valid packetby performing an ECC (Error Check Code) check, etc.

The CPU 22 stores, to the RAM 24, the data in the header part Ph of thepacket Pa determined to be valid, and also analyzes the information inthe header part Ph. According to the results of the analysis, the CPU 22displays, on the display unit 28, the transmission destination callsign, the transmission source call sign, etc. of the received packet Pa.

The above-described processing for reproducing a packet from a radiosignal received in the slow data mode is the same for both a radioapparatus that supports the fast data mode and a radio apparatus thatdoes not support the fast data mode. Therefore, no particular problemarises even when an existing radio apparatus that does not support thefast data mode receives the radio signal.

Configuration of Audio Frame in Each Communication Mode

Prior to a description of the operations for communication in the fastdata mode, a description is given of the configuration of the audioframe in the fast data mode, in comparison with the configuration of theaudio frame in the slow data mode.

As described above with reference to FIG. 3, when audio communicationand data communication are simultaneously performed in the slow datamode, i.e., the communication mode in which audio signal data isinserted into audio frames, 9 bytes of audio signal data is insertedinto each audio frame d1. Meanwhile, regarding data for datacommunication, a data block composed of a communication data portion d6,which is one of the divided 5-byte portions, and the mini-header d5added to the beginning of the communication data portion d6, is dividedinto two portions, and these two portions are respectively inserted intotwo data frames d2.

In contrast, in the case of using both the audio frames and the dataframes to transmit data for data communication in the fast data mode,i.e., the mode in which data for data communication is inserted intoaudio frames, the data to be transmitted is divided into 20-byteportions, and the mini-header d5 and so on is added to each portion soas to compose a block, and the data of the block is divided and insertedinto two adjacent audio frames d1 and two adjacent data frames d2.

Specifically, each block is 24-byte data composed of 20-byte data fordata communication, a 1-byte mini-header, 2-byte unique data, which isdescribed below, and 1-byte data to be inserted into data frames inorder to prevent the misdetection of packet loss, and this data block isdivided and inserted into two adjacent audio frames d1 (9 bytes×2) andtwo adjacent data frames d2 (3 bytes×2).

If a comparison is made between the case of inserting the audio signaldata into the audio frames d1 of the packet Pa and the case of insertingthe data for data communication into the audio frames d1, thecommunication speed of the latter case is approximately 3.5 times thecommunication speed of the former case, and the data for datacommunication can be transmitted at high speed in the latter case.

FIG. 5A shows the configuration of the audio frame in the slow datamode, and FIG. 5B shows the configuration of the audio frame in the fastdata mode. In these figures, the numbers 1 to 9 shown at the middlelevel indicate the order of the data portions constituting the 9-byteaudio frame. The type of data to be inserted in the corresponding byteposition is shown at the lower level.

As shown in FIG. 5A, in the slow data mode, the audio signal data isinserted in every one of the portions that constitute the 9-byte audioframe. In contrast, as shown in FIG. 5B, in the fast data mode, data fordata communication is inserted in the 1^(st) to 4^(th) and 6^(th) to9^(th) portions, which have 8 bytes in total, out of the portions thatconstitute the 9-byte audio frame, and unique data is inserted in the5^(th) 1-byte portion.

When the data of the audio frame shown in FIG. 5B is reproduced by aradio apparatus that supports the fast data mode, the 5^(th) 1-byte datais determined to be unique data for abnormal sound reduction based onthe information in the mini-header d5, and only the 8-byte data isretrieved from the 1^(st) to 4^(th) and 6^(th) to 9^(th) portions and isreproduced as data for data communication, whereas the 1-byte data inthe 5^(th) portion is not reproduced.

In contrast, when the data of the audio frame shown in FIG. 5B isreproduced by a radio apparatus that does not support the fast datamode, the entire 9-byte data is retrieved from the 1^(st) to 9^(th)portions, and is reproduced as audio signal data. Therefore, when theaudio signal data thus reproduced is decoded by the audio codec 14, ameaningless signal is reproduced because it is actually not an audiosignal, and consequently, the speaker 12 outputs an abnormal sound.

However, since the 5^(th) 1-byte data inserted in the audio frame isdata that is likely to cause an error when decoded by the audio codec14, the data is determined to be an error and is not output by the audiocodec 14, and accordingly audio is not output from the speaker 12.

For example, in the case where an audio vocoder from Digital VoiceSystems, Inc. (DVSI) is used as the audio codec 14 and two-digithexadecimal data “0x02” is inserted in the 5^(th) 1-byte portion, thedata is determined to be an error at the time of decoding by the audiocodec 14, and no signal is output. Incidentally, audio vocoders fromDVSI use a vocoder chip that employs the Advanced Multi-Band Excitationmethod as audio compression technology.

Therefore, when the data of the audio frame shown in FIG. 5B isreproduced by an existing radio apparatus that does not support the fastdata mode, an error occurs in the audio codec 14, and consequently nosignal is generated, and no abnormal sound is output from the speaker12.

Operations for Communication in Fast Data Mode

Next, with reference to FIG. 6 and FIGS. 1 to 5B described above, adescription is given of the operations for communication in the fastdata mode. FIG. 6 is a flowchart showing processing performed by thecontroller 21 of the radio apparatus 1 that has received a radio signal.

Note that the descriptions of the operations that the user performsbefore starting the communication, such as the operation for storing theinformation necessary for the communication to the non-volatile memory25, the operation for designating the transmission destination call signand the call sign of the transmission destination repeater, and so onare omitted, because they are the same as in the communication performedin the slow data mode.

In the case of operating the radio apparatus 1 in the fast data mode,the user switches the mode switch 33 provided in the operation unit 26to the fast data mode. The controller 21 causes the radio apparatus 1 tooperate in the fast data mode according to the switch of communicationmode.

When instructed to perform transmission in the fast data mode by theuser operation, the controller 21 instructs the transmission unit 15 toperform transmission in the fast data mode. Upon being instructed by thecontroller 21 to perform transmission, the transmission unit 15 startsgenerating the packet Pa.

Specifically, the transmission unit 15 generates a packet in which datafor data communication is inserted in each of the audio frames d1 andeach of the data frames d2. Furthermore, as shown in FIG. 5B, data fordata communication is inserted into the 8-byte portion out of the audioframe d1 except the 5^(th) 1-byte portion.

At this time, the 5^(th) 1-byte data portion is transmitted from thecontroller 21 to the transmission unit 15. Also, according to aninstruction from the controller 21, information indicating that data fordata communication is inserted in the audio frames d1, and that uniquedata is inserted in the 5^(th) 1-byte portion of the audio frame, iswritten into the mini-header d5 (see FIG. 3). The packet Pa thusgenerated is furthermore converted into high-frequency signals by thetransmission unit 15, and they are transmitted from the antenna 17 asradio signals.

The controller 21 of the radio apparatus (the communication partystation) 1 d, which has received radio signals transmitted from theradio apparatus (the user's own station) 1 a operating in theabove-described fast data mode, processes the packet Pa according to theflowchart shown in FIG. 6.

First, the controller 21 retrieves the data in the data frames d2 fromthe data of the packet Pa, which has been reproduced by the receptionunit 18 from the radio signals, and then writes it into a built-inregister (not shown in the drawings) (Step S11). The controller 21analyzes the information in the mini-header d5, and determines whetheror not the packet Pa is a packet transmitted in the fast data mode (StepS12).

The controller 21 confirms that the data for data communication isinserted in the audio frames d1 (Yes in Step S13), and instructs thereception unit 18 to retrieve the 8-byte data for data communicationfrom the audio frames d1, while excluding the 5^(th) 1-byte data fromthe audio frames d1 (Step S14).

Next, the controller 21 concatenates the data portions retrieved fromtwo adjacent audio frames d1 and two adjacent data frames d2 in reverseorder to how the block is created as described above, therebyreproducing the data for data communication (Step S15). The data fordata communication thus reproduced is output to the interface unit 19.

The controller 21 instructs the interface unit 19 to transfer thereproduced data for data communication to the external device (StepS16), and the interface unit 19 outputs the reproduced data for datacommunication to the external device 31 according to the instruction.

Incidentally, in the case where the radio apparatus 1 receives radiosignals in the slow data mode, the controller 21 confirms in Step S13that audio signal data is inserted in the audio frames d1 (No in StepS13), and instructs the reception unit 18 to retrieve all of the 9-bytedata included in the audio frames d1 (Step S17).

Next, the controller 21 instructs the audio codec 14 to decode the audiosignal data retrieved from the reception unit 18 (Step S18), and theaudio codec 14 performs audio signal decoding according to theinstruction from the controller 21. The audio signal decoded andconverted into an analogue audio signal is output from the speaker 12.

In parallel with Steps S17 and S18, the controller 21 concatenates thedata portions retrieved from the data frames d2 and stored in theregister, thereby reproducing the data for data communication (StepS19). The data for data communication thus reproduced is output to theinterface unit 19.

Next, the controller 21 performs the above-described Step S16, in otherwords instructs the interface unit 19 to transfer the reproduced datafor data communication to the external device 31, and the interface unit19 outputs the reproduced data for data communication to the externaldevice 31 according to the instruction.

As described above, with use of the radio communication system accordingto the present embodiment, even in the case where an existing radioapparatus that does not support the fast data mode receives a packet inwhich data for data communication is inserted in the audio frames, theabnormal sound generated by the speaker can be reduced to such a levelthat is not problematic in practical use.

Consequently, even in the case of using a mix of a radio apparatus thatsupports the fast data mode and an existing radio apparatus that doesnot support the fast data mode, both radio apparatuses can be usedwithout a problem.

According to the embodiment above, the unique data “0x02” is insertedinto the 5^(th) 1-byte portion of the audio frame. However, the positionof insertion and data to be inserted is not limited to the above. In thecase of using an audio codec other than the audio vocoder used in thepresent embodiment, the position and the contents of data to be insertedinto the audio frames may be changed according to the audio codec thatis used. The point is to select data that is likely to cause an errorwhen decoded by the audio codec.

Although the present invention has been fully described by way ofexample with reference to the accompanied drawings, it is to beunderstood that various changes and modifications will be apparent tothose skilled in the art.

Therefore, unless otherwise such changes and modifications from thescope of the present invention hereinafter defined, they should beconstrued as being included therein.

What is claimed is:
 1. A radio communication system including at leasttwo radio apparatuses, each radio apparatus is configured to: generate apacket including a header part containing identifier data identifying atleast a transmission destination radio station and a transmission sourceradio station; and a data part in which an audio frame and a data frame,each having a predetermined length, are consecutively arranged one afteranother, to insert audio signal data into the audio frame of the packetand to insert data other than the audio signal data into the data frameof the packet, and to thereafter convert the packet into a radio signaland transmit the radio signal; and receive the radio signal, toreproduce a packet from the radio signal, to retrieve the audio signaldata from the audio frame of the packet, and to retrieve the data otherthan the audio signal data from the data frame of the packet; and eachradio apparatus comprising: an audio codec configured to generate adigital audio signal by performing A/D conversion and encoding on ananalogue audio signal, and to reproduce an analogue audio signal byperforming decoding and D/A conversion on a digital audio signal; and acontroller configured to instruct the radio apparatus to generate apacket, and to reproduce a packet from a received radio signal, wherein,when communication is performed in a fast data mode in which data fordata communication to be transmitted, instead of audio signal data, isinserted in the audio frame, the radio apparatus serving as a sendergenerates, according to an instruction from the controller, a packet inwhich the data for data communication is inserted in positions in theaudio frame excluding a given position, and in the data frame, andunique data is inserted in the given position in the audio frame, andthe controller serving as a recipient, which has received a radiosignal, instructs the radio apparatus to retrieve data portions otherthan the unique data from the audio frame and the data frame of thepacket, which has been reproduced, and reproduces the data for datacommunication by concatenating the retrieved data portions.
 2. The radiocommunication system according to claim 1, wherein the data frame has amini-header that contains information about data to be inserted in thedata frame, and when communication is performed in the fast data mode,the radio apparatus inserts the data for data communication in thepositions in the audio frame excluding the given position, and writes,in the mini-header, the information indicating that the unique data isinserted in the given position in the audio frame.
 3. A radio apparatusconfigured to generate a packet including a header part containingidentifier data identifying at least a transmission destination radiostation and a transmission source radio station; and a data part inwhich an audio frame and a data frame, each having a predeterminedlength, are consecutively arranged one after another, to insert audiosignal data into the audio frame of the packet and to insert data otherthan the audio signal data into the data frame of the packet, and tothereafter convert the packet into a radio signal and transmit the radiosignal, the radio apparatus, comprising: an audio codec configured togenerate a digital audio signal by performing A/D conversion andencoding on an analogue audio signal; and a controller configured toinstruct the radio apparatus to generate a packet, wherein, whenoperating in a fast data mode in which data for data communication to betransmitted, instead of audio signal data, is inserted in the audioframe, the radio apparatus generates, according to an instruction fromthe controller, a packet in which the data for data communication isinserted in positions in the audio frame, excluding a given position,and in the data frame, and in which unique data is inserted in the givenposition in the audio frame.
 4. The radio apparatus according to claim3, further configured to receive the radio signal, reproduce the packetfrom the radio signal, and retrieve audio signal data from the audioframe of the packet and data other than the audio signal data from thedata frame of the packet, wherein, when a radio signal transmitted inthe fast data mode is received, the controller instructs the radioapparatus to retrieve data portions other than the unique data from theaudio frame and the data frame of the packet, which has been reproduced,and reproduces the data for data communication by concatenating theretrieved data portions.
 5. A radio communication method for a radiocommunication system including at least two radio apparatuses, one ofthe at least two radio apparatuses being configured to generate a packetincluding a header part containing identifier data identifying at leasta transmission destination radio station and a transmission source radiostation; and a data part in which an audio frame and a data frame, eachhaving a predetermined length, are consecutively arranged one afteranother, and to convert the packet into a radio signal and transmit theradio signal, and another one of the at least two radio apparatusesbeing configured to receive the radio signal and reproduce a packet fromthe received radio signal, the radio communication method comprising thesteps of: in a radio apparatus serving as a sender, generating a packetin which data for data communication is inserted in positions in theaudio frame, excluding a given position, and in the data frame, andunique data is inserted in the given position in the audio frame; andconverting the packet thus generated into a radio signal, andtransmitting the radio signal, and in a radio apparatus serving as arecipient, receiving the radio signal; reproducing a packet from thereceived radio signal; retrieving data portions other than the uniquedata from the audio frame and the data frame of the reproduced packet;and reproducing data for data communication by concatenating theretrieved data portions.
 6. A packet generation method for a radioapparatus that performs communication with another radio apparatus byusing a packet including a header part containing identifier dataidentifying at least a transmission destination radio station and atransmission source radio station; and a data part in which an audioframe and a data frame, each having a predetermined length, areconsecutively arranged one after another, the packet generation methodcomprising the step of: in the radio apparatus, determining whether ornot the communication is performed in a fast data mode; whencommunication is performed in a fast data mode in which data for datacommunication to be transmitted, instead of audio signal data, isinserted in the audio frame, generating a packet in which data for datacommunication is inserted in positions in the audio frame, excluding agiven position, and in the data frame, and unique data likely to causean error when decoded by an audio codec is inserted in the givenposition in the audio frame; and when communication is not performed ina fast data mode, generating a packet in which audio signal data isinserted in the audio frame, and data for data communication is insertedin the data frame.
 7. A method for reproducing data from a packetperformed by a radio apparatus that is configured to receive a radiosignal containing a packet generated by the packet generation methodaccording to claim 6, and to reproduce the packet from the radio signal,the method comprising the steps of: retrieving data portions other thanthe unique data from the audio frame and the data frame of thereproduced packet; and reproducing the data for data communication byconcatenating the retrieved data portions.